The present invention relates generally to method and apparatus for making containers from precut blanks of paper-like material by rolling a precut blank and sealing angularly overlapping end portions of the rolled container blank and more particularly to new and improved method and apparatus of the type described employing a rotatable mandrel for rolling a precut container blank at a first station of the mandrel and for retaining the rolled container blank thereon for sealing overlapping end portions thereof at a second different station of the mandrel.
It is a primary aim of the present invention to provide new and improved method and apparatus for rolling and sealing container blanks of paper-like material.
It is another aim of the present invention to provide a new and improved paper container machine for rolling a paper-like container blank onto a mandrel at a first station of the mandrel and for sealing overlapping end portions of the rolled container blank at a subsequent station of the mandrel. In accordance with the present invention, an indexing table having an annular arrangement of a plurality of mandrels and adapted to be periodically indexed, is employed for indexing each mandrel to successive rolling and sealing stations.
It is another aim of the present invention to provide new and improved method and apparatus for forming a longitudinal container seam in overlapping end portions of a rolled container blank of paper, synthetic material or the like. The present invention has notable use in rolled paper-like container manufacturing systems, in which a time interval is provided between the rolling and sealing steps. In the past, the overlapping end portions of a rolled container blank have been held, for example as described in the Federal Republic of Germany Patent, GT No. 1,288,416 with clamps associated and rotated with a rolling mandrel and mechanically operated independently of a sealing cheek or blade operated for sealing the overlapping end portions together. The provision of such clamps and the mechanism required for operating the clamps is expensive, and in accordance with the present invention, such clamps are replaced by vacuum retention means for holding the overlapping end portions of the rolled blank in position for sealing. For that purpose, a container rolling mandrel is provided with two angularly spaced axially extending rows of vacuum ports for separate vacuum retention of the two overlapping ends of a container blank as it is rolled onto the mandrel and whereby the overlapping ends are held in position to be sealed as desired, for example, at a succeeding sealing station to which the mandrel is indexed. When the mandrel is rotated to roll a precut container blank onto the mandrel, a leading edge of the precut container blank is initially held in place against the mandrel by a row of low pressure or vacuum ports timely connected to a suitable low pressure source. A second row of low pressure ports is arranged on the mandrel adjacent to but angularly spaced from the leading edge row of ports for retaining the trailing edge of the container blank against the mandrel after the paper-like container blank has been rolled onto the mandrel. The trailing edge row of vacuum ports are likewise timely connected to the low pressure source after the leading edge row of ports and so as to avoid reducing the vacuum retention of the leading edge of the container blank.
Thus, according to the present invention, each of two rows of vacuum retention ports of the mandrel are selectively connected to a low pressure source so that the leading edge row of vacuum ports is effective as soon as the container blank rolling operation begins, and the trailing edge row of vacuum retention ports is effective at the earliest after the leading edge row of ports is covered by the container blank and at the latest after the container blank rolling step is completed and before a roll guide for the blank is withdrawn. Furthermore, the two rows of retention ports are selectively connected to a low pressure source in accordance with the invention so that the rolled paper-like container blank is firmly held on the mandrel until overlapping edge portions thereof have been effectively sealed together.
A better understanding of the invention will be obtained from the following detailed description and the accompanying drawings of an illustrative application of the invention.